As an exothermic body for metal vapor deposition, there has hitherto been known a boat form (hereinafter referred to as a “boat”) in which a cavity is formed in an upper surface of a ceramics sintered body mainly comprising, for example, boron nitride (BN), aluminum nitride (AlN) or titanium diboride (TiB2) (patent document 1), and as an example of a commercially available product thereof, there is “BN Composite EC”, a trade name, manufactured by Denki Kagaku Kogyo Kabushiki Kaisha. There is also a form having no cavity. As for the usage of these, both ends of the boat are connected to electrodes with clamps, and voltage is applied thereto, which allows it to generate heat to melt and evaporate a metal such as aluminum wire rods fed in the cavity, thereby obtaining a vapor deposition film, followed by cooling.
In such a boat, the molten metal corrodes the boat to fluctuate the effective sectional area and electric resistance, resulting in failure to give a sufficient vapor deposition speed. For example, when the molten metal is aluminum, corrosion occurs according to the following reaction equations:Al(s)+TiB2(s)→Al(l)+TiB2(l)13Al(s)+12BN(s)→AlB12(s)+12AlN(s)
Further, the corrosion locally occurs at a cavity portion in many cases, that is, spreading by wetting of molten aluminum is localized to a center portion of the cavity. Accordingly, the film thickness distribution of a material to be vapor deposited comes failed to be sufficiently given, reaching the end of life. In order to prolong the boat life, what is necessary is just to increase the relative density of the boat to 95% or more (patent document 2). However, this necessitates a high pressure as high as 100 to 300 MPa, so that the cost of equipment increases, and productivity is also inferior. On the other hand, there is also a proposal of devising a method for cutting out of a hot press sintered body so that anisotropy does not occur in crystal orientation of BN in the boat (patent document 3). However, in spite of these improvements, the above-mentioned reactions gradually proceed under high temperature during aluminum vapor deposition, and there has been still room for prolonging the life.
[Patent Document 1] JP-B-53-20256
[Patent Document 2] JP-A-60-21866
[Patent Document 3] JP-B-5-66906